Electrical switchgear with electro-dynamic strengthening of the contactpressure



Oct. 27, 1964 F. HEUPEL ETAL 3,154,662

ELECTRICAL SWITCHGEAR WITH ELECTRO-DYNAMIC STRENGTHENING OF THE CONTACT-PRESSURE INVENTORS FrLedrz'ch HeupeL 569mm" Kofoll /pLQI/uu,

Filed June 18,

L 29 l wiw ATTORNEYS United States Patent ELECTRECAL W1TCHGEAR WTTH ELECTED-DY- NAMHC STRENGTHENING 6F THE CGNTACT- PREURE Friedrich Heupei, Frankfurt am Main-Echenheim, Germany, and Sigrnar Kotoii, Neuenhoi, Switzeriand, assignors to Brown, Boveri & Cie, Ahtiengeseilschaft, Mannheim, Germany, a joint-stock company Fiied June 13, 1962, Ser. No. 203,303 Claims priorit application Germany dune 2t), 1961 3 Claims. (Cl. 200-170) This invention relates to electrical switchgear apparatus and more particularly to electrical switches having conductor pieces forming parallel current paths through the same and a movable contact bridge for each path. The object of the invention, in general, is to provide an improved switch construction of the type described and wherein the conductor pieces and their respective contact bridges forming these parallel current paths are mutually attracted by electro-dynamic forces derived from the current passing through the conductor pieces and in such manner that the conductor pieces and the contact bridges of the respective current paths are always maintained at a very small distance apart thus assuring a high degree of mutual attraction and a corresponding high degree of contact pressure between the conductor pieces of the two current paths and their respective contact bridges.

It is known, with electrical switchgear, and more especially with those having input and output connections, and switch components designed for higher currentstrengths, that there results a strengthening of the contactpressure, especially in the case of a short-circuit, due to the electro-dynamic effects of the current. Thus one employs, for example, with disconnecting i.e. isolating switches, two parallel switch-blades per current-path between the ends of which, both stationary switch-pieces are located or, respectively, will be located. Due to the current strength these blades, lying parallel to one another, become mutually attracted by the ensuing electro-dynamic forces which results in a strengthening of the contact pressure. There is, however, the disadvantage that in the case of small units one cannot arrange the parallel blades in the desired relative positions as the fixed contact which is to be between them, cannot be made sufficiently small. In addition, the recognized switchblade arrangement for load switches is not suitable. In general here, for the main contact positions, switch-pieces with pressure-contacts are necessary, by reason of the greater frequency of switch-operations and by reason of the particular switchmechanics which must result from the periodic opening and closing of the main and secondary-switch-pieces.

The present invention is directed to a load switch which provides for electro-dynamic strengthening of the contact pressure, the switch being provided with parallel current paths which are opened and closed respectively by means of contact bridges, and the two current paths represented by elongated conductor pieces being arranged both spacially and electrically in parallel with a very small gap therebetween. Because of this very small gap, the mutually attractive forces between the elongated conductor pieces forming the two current paths and their contact bridges becomes correspondingly high and hence, results in a high degree of contact pressure between the contact bridges and their respective conductor pieces. In accordance with the invention, the pressure contact points of the contact bridges lie on the same sides of the bridges, i.e. also on the same sides of the conductor pieces forming the two current paths. Moreover, the contact bridge associated with one of the current paths is connected by a spring to the operating member for the contact bridges and the conductor pieces associated with this contact bridge are supported so as to be immovable. The con- "ice tact bridge associated with the other current path is rigidly connected to the operating member for the contact bridges and the conductor pieces associated with this latter contact bridge are spring supported. The positioning of the springs is so arranged that the spring derived forced associated with the spring loaded contact bridge acts in opposition to the spring derived force associated with the spring loaded conductor pieces.

The foregoing objects and advantages of the invention will become more apparent from the following detailed description of a preferred embodiment thereof and from the accompanying drawings wherein:

FIG. 1 is a view of the improved switch structure in side elevation, this view being limited, in the interest of simplifying the drawing, to those parts of the switch struc ture which characterize the invention; and

FIG. 2 is a vertical section taken on line 2-2 of FIG. 1.

Referring now to the drawings, the improved electrical load switch is comprised of two current paths I and II therethrough arranged electrically in parallel. Current path I is constituted by two elongated conductor pieces 10 and 11 in the form of bars arranged along a rectilinear line and with end portions 10a, 1101 located in confront ing spaced relation. These end portions 10a, 11a are adapted to be connected and disconnected by means of a contact bridge 12. The elongated conductor pieces 10 and 11 are secured rigidly near their ends 10a, 11a to fixed supports 13, 14 respectively, which may be made of insulating material and thus the conductor pieces 10, 11 are rendered substantially immovable.

Current path II is also constituted by two elongated conductor pieces 15, 16 in the form of bars arranged along a rectilinear line located beneath conductor pieces 10, 11 and with end portions 150, 16a located in confronting spaced relation. Thus, the conductor pieces 10, 11 constituting path I lie spacially and electrically parallel to conductor pieces 15, 16 constituting path II and are spaced from each other by a small distance 7'. The end portions 15a, 16a are adapted to be connected and disconnected by means of a contact bridge 17. Unlike the rigidly mounted conductor pieces 10, 11, the end portions 15a, 16a of conductor pieces 15, 16 are supported on springs 18, 19 respectively which engage the end portions 15a, 16a from beneath so as to urge them in the direction of the upper conductor pieces 16, 11, as indicated by the arrows.

The two contact bridges 12 and 17 are arranged for operation together by an actuating member 20 which is arranged for movement in a direction normal to the conductor pieces 1%, 11 and 15, 16. Contact bridge 17 is secured rigidly with respect to the actuating member 20 but the other contact bridge 12 is mounted in a yielding manner with respect to actuating member 2t This yieldable mount is established by means of a plate 21 upstanding on the actuating member 20 and secured rigidly thereto. Contact bridge 12 includes a pin 22 projecting laterally and which engages in an elongated slot 23 in plate 21 extending in the direction of movement of the actuating member 20. A loading spring 24 under compression has its upper end in abutment with a flange 25 extending laterally outward from plate 21 and its lower end in abutment with the upper face of contact bridge 12. Thus, spring 24 exerts a loading force on contact bridge 12 in the direction of the rigidly mounted conductor piece ends 19a, 11a as indicated by the arrow.

The general result obtained by the respective mountings of the conductor pieces 1%, 11 and 15, 16 and of the contact bridges 12, 17 is that contact bridge 12 is spring loaded downwardly in the direction of the immovable conductor piece ends 10a, 11a, and the conductor piece ends 150, 16a are spring loaded upwardly in the direction of the contact bridge 17. Thus, the directions of spring-action of the spring-loaded bridge 12 and the springloaded conductor piece ends 15a, 16a are in opposition.

To cause the contact bridges 12 and 17 to engage their corresponding conductor piece ends 10a, 11a and 15a, 16a respectively, the actuating member 20 is moved downwardly to the position indicated in FIG. 1. Since the contact bridge 17 is secured immovably with respect to the actuating member 20, the electro-dynamically produced force derived from the current passing along the paths I and II takes effect upon the spring-loaded contact bridge 12 whereupon the latter is induced to exert a higher degree of pressure downwardly against the im movable conductor piece ends 10a, Ila than is normally exerted by spring 24. p

In a similar manner, since the contact bridge 17 is secured immovably with respect to actuating member 263, the electro-dynamically produced force derived from the current passing along the paths I and II also takes effect upon the spring loaded conductor piece ends 15a, 16a which are thus caused to exert a higher degree of pressure upwardly against the then immovable contact bridge 17 than is normally exerted by the springs 18, 119.

It will thus be seen that in accordance with the invention, the conductor pieces forming the two component current paths I and II are arranged parallel to each other with a minimum gap 1, and this minimum gap is maintained electro-dynamically and with increased pressure between the contacts due to the fact that the pressure contact positions are arranged on the same sides of the contact bridges 12 and 17, namely, at the lower sides or faces in accordance with the illustrated embodiment of the invention which is to say that in such embodiment the pressure contact positions of the conductor piece ends 10a, 11a and 15a, 16:: are located on their upper sides or faces.

Because of the fact that the improved switch construction in accordance with the invention enables the conductor elements of the two switch paths I and II to be mutually attracted by electro-dynamic forces and maintained at a small distance apart, these electro-dynarnically derived forces supplementing the normal forces derived from springs 18, 19 and 24 to increase the contact forces between the contact bridges 12 and 17 and their respective conductor piece ends 10a, 11a and 15a, 16a, especially under higher than normal current loads passing through the switch, one is enabled to control the flow of substantially higher short-circuit currents through the switch without damage to the contacts than is possible with the prior known constructions. There is also the further advantage in that the switch operates with a pressure-contact.

In order to provide for higher current loads through the switch, the spring loaded components which have been described can be further sub-divided so that there will exist several parallel contact points in each of the two current paths.

We claim:

1. In an electrical load switch, the combination comprising means establishing in said switch two current paths electrically and spacially in parallel and with a small spacial gap therebetween, each said current path being constituted by elongated conductor pieces in alignment and having end portions arranged in confronting spaced relation and including a contact bridge adapted to be engaged with and disengaged from the end portions of said conductor pieces, the pressure contact positions of said contact bridges with respect to the end portions of the conductorpieces being located on the same sides of said bridges, means mounting the elongated conductor pieces constituting a first one of said current paths such that said conductor pieces and the confronting end portions thereof are substantially immovable, an actuating member for said contact bridges, means including spring means mounting a first one of said contact bridges on said actuating member, said spring means serving to load said contact bridge into engagement with the substantiaily immovable end portions of the conductor pieces forming said first current path, means mounting the second of said contact bridges rigidly on said actuating member, and means including spring means mounting the elongated conductor pieces constituting the second of said current paths such that said conductor pieces and the confronting end portions thereof are loaded into engagement with said second and rigidly mounted contact bridge, the directions of the spring loading forces associated respectively with said first contact bridge and with the conductor pieces constituting said second current path being in opposition to one another.

2. An electrical load switch as defined in claim 1 wherein said actuating member includes a plate member extending normal to said conductor pieces, and said means for mounting said first contact bridge includes a compression spring having one end thereof in abutment with a laterally extending stop on said plate member and the opposite end thereof in abutment with said first contact bridge, said first contact bridge also being provided with a pin projecting outwardly therefrom and which is entered into a slot in said plate member, said slot being elongated in the direction of movement of said plate member.

3. An electrical load switch as defined in claim 1 wherein the spring loaded parts of each current path are further sub-divided into conductor pieces lying spacially parallel to one another.

References Cited in the file of this patent FOREIGN PATENTS 1,056,696 Germany May 6, 1959 

1. IN AN ELECTRICAL LOAD SWITCH, THE COMBINATION COMPRISING MEANS ESTABLISHING IN SAID SWITCH TWO CURRENT PATHS ELECTRICALLY AND SPACIALLY IN PARALLEL AND WITH A SMALL SPACIAL GAP THEREBETWEEN, EACH SAID CURRENT PATH BEING CONSTITUTED BY ELONGATED CONDUCTOR PIECES IN ALIGNMENT AND HAVING END PORTIONS ARRANGED IN CONFRONTING SPACED RELATION AND INCLUDING A CONTACT BRIDGE ADAPTED TO BE ENGAGED WITH AND DISENGAGED FROM THE END PORTIONS OF SAID CONDUCTOR PIECES, THE PRESSURE CONTACT POSITIONS OF SAID CONTACT BRIDGES WITH RESPECT TO THE END PORTIONS OF THE CONDUCTOR PIECES BEING LOCATED ON THE SAME SIDES OF SAID BRIDGES, MEANS MOUNTING THE ELONGATED CONDUCTOR PIECES CONSTITUTING A FIRST ONE OF SAID CURRENT PATHS SUCH THAT SAID CONDUCTOR PIECES AND THE CONFRONTING END PORTIONS THEREOF ARE SUBSTANTIALLY IMMOVABLE, AN ACTUATING MEMBER FOR SAID CONTACT BRIDGES, MEANS INCLUDING SPRING MEANS MOUNTING A FIRST ONE OF SAID CONTACT BRIDGES ON SAID ACTUATING MEMBER, SAID SPRING MEANS SERVING TO LOAD SAID CONTACT BRIDGE INTO ENGAGEMENT WITH THE SUBSTANTIALLY IMMOVABLE END PORTIONS OF THE CONDUCTOR PIECES FORMING SAID FIRST CURRENT PATH, MEANS MOUNTING THE SECOND OF SAID CONTACT BRIDGES RIGIDLY ON SAID ACTUATING MEMBER, AND MEANS INCLUDING SPRING MEANS MOUNTING THE ELONGATED CONDUCTOR PIECES CONSTITUTING THE SECOND OF SAID CURRENT PATHS SUCH THAT SAID CONDUCTOR PIECES AND THE CONFRONTING END PORTIONS THEREOF ARE LOADED INTO ENGAGEMENT WITH SAID SECOND AND RIGIDLY MOUNTED CONTACT BRIDGE, THE DIRECTIONS OF THE SPRING LOADING FORCES ASSOCIATED RESPECTIVELY WITH SAID FIRST CONTACT BRIDGE AND WITH THE CONDUCTOR PIECES CONSTITUTING SAID SECOND CURRENT PATH BEING IN OPPOSITION TO ONE ANOTHER. 